1. Field of the Invention
This invention relates to an apparatus and a method of depositing magnetic thin films used for the magnetic recording media in a mass production, direct current sputtering process and an improved magnetic recording disk product thereby.
2. Description of the Prior Art
The magnetic films that have been used in recording disk and tape systems have been usually particulate in nature, the magnetic particles being embedded in a binder material and then applied to the substrate. Recently, sputtered and evaporated thin film media have been investigated and utilized for commercial data storage systems. The advantages of thinness, low defect level, smoothness and high induction are particularly adaptable to high recording densities at the desirable low flying heights of the head pieces. To provide high density recording it has been recognized that the thin films should exhibit high magnetization, high coercivity, and a square hysteresis loop. Examples of thin film material have included cobalt nickel thin films that have been deposited upon sublayer films of gold to epitaxially orientate the "C" axis of the cobalt/nickel in the plane of the film.
There have been other suggestions to evaporate cobalt films onto a chromium sublayer to increase the coercivity of the cobalt film. Chromium/cobalt deposit film structures have also been suggested using RF diode sputtering. The chromium layer serves as a nucleating layer to provide nucleating centers around which a subsequent magnetic film may grow. Thus, the layer of nucleating material serves to form small agglomerations that are evenly dispersed over the surface of an insulating substrate.
Substrates of glass or aluminum alloys have been suggested for subsequently receiving sputtered deposited layers of chromium cobalt, such as set forth in the article "Sputtered Multi-Layer Films for Digital Magnetic Recording" by Maloney, IEEE Transactions on Magnetics, Volume MAG-15, 3, Jul. 1979. Examples of cobalt nickel magnetic thin films are suggested in the article "Effect of Ion Bombardment During Deposition on Magnetic Film Properties" by L. F. Herte et al., Journal of the Vacuum Society Technology, Volume 18, No. 2, Mar. 1981. Finally, the use of a protective layer of carbon in a cobalt chromium structure is suggested in "The Optimization of Sputtered Co-Cr Layered Medium for Maximum Aerial Density" by W. T. Maloney, IEEE Transaction Magnetics Volume Mag-17, No. 6, Nov. 1981. The prior art has recognized the importance of reducing the head-gap, the flying height and the medium thickness but to date has not suggested a realization of a low cost commercial process of producing improved magnetic film disks on a production basis to realize the theoretical advantages of certain research results. Thus, there is still a need to improve both the apparatus and process of producing and the characteristics of thin magnetic film disks for commercial utilization.